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What Is EP Grease Best Used For?

Featured image for "What Is EP Grease Best Used For?" blog post. Dump truck and tractor in gravel pit.

If you’ve asked yourself the question “What is EP grease best used for?”, this detailed blog post will shed light on this subject.

The acronym “EP” simply means extreme pressure.

Log mover in forest.
Logging equipment is exposed to a tremendous amount of shock loads and extreme pressure. An EP grease with a high Timken OK Load would be a useful lubricant in these conditions.











Characteristics of an EP Grease

The goal of any lubricant is to keep two metal surfaces from coming in contact with each other. When those two metals surfaces are put under extreme shock loading or high pressure, a regular non-EP grease will be pushed past its limit whereby the protective film can no longer withstand the shock load or high pressure, and thus breaks. When this happens, those two metal parts literally come into physical contact with each other, causing unwanted wear and friction.

To overcome such a situation, a lubricant manufacturer will take their normal grease and engineer in extreme pressure additives that may come in the form of liquid or solid lubricants. Solid lubricants such as molybdenum disulfide and graphite are consider extreme pressure additives. Some extreme pressure liquid additives include liquid moly, antimony, etc.

These additives were designed to withstand very high pressures and shock loads. When the basic film of grease and oil would rupture under such tremendous shock loads, these solid and/or liquid EP additives come into play and act as an extra barrier of protection to keep two metal surfaces from coming into physical contact with each other.

A large yellow excavator machine at work.
Excavating equipment will require an extreme pressure grease that can withstand shock loading, extreme pressure, and protect parts from excessive dust and dirt. The adhesive/cohesive feature is helpful here.








These extreme pressure agents literally bond themselves to the surface of the metal, thus preventing metal-to-metal contact. Not only do they withstand heavy shock loads, but they also can reduce friction and wear, greatly extending the life of the parts they are protecting.

Also, when considering EP greases one needs to look at the grease’s consistency and the actual base oil type, viscosity of the base lubricating oil and thickener utilized in the formulation. If the machinery in question operates in difficult and extreme environments where parts will be exposed to heavy shock loads, consider the option of using an EP grease that is formulated with a heavier base fluid and a calcium/lithium complex based thickener.

To keep a grease from pounding or squeezing out when exposed to extreme pressure and shock loads, it can be helpful that such a grease utilizes adhesive and cohesive additives. These additives give a grease a tacky, or sticky, characteristic.

A tacky grease typically is very difficult to squeeze or pound out. Some added benefits to a grease with adhesive and cohesive properties is its ability to create a very resistant barrier to contamination. Additionally, such a grease will offer superior water washout resistance.

Front loading excavator loading a dump truck.
When looking at an EP grease’s specifications, check the Timken OK Load rating. A 100 Timken OK Load screams out “Hey, use me! I can handle extreme pressure better than any other grease!”

Specifically, What is EP Grease Best Used For?

An extremely high performance, high quality EP  synthetic grease is typically formulated to be used in applications where industrial machinery will be operating in very extreme conditions, such as high shock loading, high heat, and moisture.

An EP grease is a perfect choice for chassis points, universal joints, pins, bearings, bushings, slide and cam mechanisms, etc. Any piece or equipment or part that is continually subjected to heavy shocks and loads will be perfect for an EP grease.

If the grease utilizes the solid lubricant molybdenum disulfide, it will offer outstanding protection against scoring of surfaces that either slide, turn, or are oscillating when exposed to extreme loads and heavy shocks. An EP grease is intended for protecting heavily loaded components during the most extreme operating conditions.

Sandy Construction Site Large Dump Truck. Moving Dirt.
Large dump trucks carrying heavy loads put the suspension components through torturous tests. Unless a superior extreme pressure grease is utilized, grease could be squeezed out, causing dangerous metal-to-metal contact.









It is important to know that molybdenum disulfide, when it has fully plated itself to metal surfaces, can absorb an astounding 500,000 pounds per square inch.

Treating a grease with 5% molybdenum disulfide will provide extra protection against friction, scuffing, and wear. By reducing friction, one is lowering temperatures in bearings, resulting in longer equipment life and less grease consumption.

An EP grease can and should be designed for extreme pressure but all function well in a broad operating temperature range. It should provide extended service even if a part is exposed to high temperature. The vast majority of most greases have dropping points between 280 and 380 degrees. A high performance grease like the one recommended in this post offers a dropping point of 630 degrees F. Here is another factor to consider when looking to provide maximum high temperature and extreme pressure protection for your hard working equipment.

Water Resistance Is A Must for an EP Grease

When asking the question” What is EP grease best used for?”, you must keep in mind that for a grease to be truly considered an EP grease, it must be water resistant. If an EP grease is not engineered to offer superior water resistance, then when the grease is exposed to water and moisture, its extreme pressure capabilities will be vastly reduced. Here is an example of how it is important to have a complete understanding and vision of the type of conditions a piece of equipment will be exposed to. It becomes an effort in futility if one purchases and invests in a grease with extreme pressure capabilities but offers poor water resistance.

You may wonder why water resistance is an important feature for an EP grease. There is a water resistance test called the ASTM D-1264 Water Washout Test. Your conventional extreme pressure greases on the market that have been put through this test typically score 10% water washout. The lower the number, the more resistant the grease is to washing away when exposed to water.

Yellow excavator machine constructing sea defenses on the beach.
Ocean dredging exposes metal parts to extreme dosages of water and corrosive salt. It is absolutely critical that an EP grease be totally waterproof. If not, expect the grease to be literally washed away, exposing critical parts to potential failure.










Many grease thickeners that are used to create a grease are made up of soap-based thickeners. Imagine if an extreme amount of water is exposed to soap. In simplistic terms, water will literally wash away the soap. Of course, in the case of the manufacturing of greases, we can say that soap is added to the oil to create a grease. The soap thickens the oil to give it its consistency.

Added to these two components, the oil and the thickener, are various additives. These additives can impart water resistance to the grease. Like all lubricants, you get what you pay for. If the goal is to utilize a grease that is extremely water resistant and waterproof, then such a grease requires specialized thickeners and additives to build such a lubricant.

If a grease is used that is not considered a water resistant grease, but is an extreme pressure grease, and the thickener type is soap-based such as a simple lithium-soap grease, then what do you think will happen if an unusual amount of water is suddenly exposed to that grease? If an inordinate amount of water stays in contact with a conventional lithium  grease, eventually much of the grease and its additives will literally be washed away. A better choice for a water resistant grease would be a thickner type such as a calcium lithium complex combination .

If this happens, then unfortunately when metal parts are exposed to extreme shock loads and extreme pressure, the grease that was washed away by the water is no longer present to protect the two metal surfaces from coming in contact with each other.

Excavator in muddy water.
A superior EP grease should have a water washout rating of less than 2%. Such an EP grease will provide extreme pressure protection anywhere and at any time without concerns of water contamination.









Important Specifications to Look for in an EP Grease

For the sake of this blog post, lets take a look at a specific EP grease that is available today on the market that offers amazing water resistance and extreme pressure capabilities, High Melting Point Grease.

To determine a grease’s extreme pressure capabilities, there is an industry standard test designated ASTM D-2509 commonly known at the Timken OK Load Test. The higher the number scored, the better a grease’s ability to withstand extreme pressure. Typical EP greases on the market average 35 to 55 pound Timken OK Load results when put through this extreme pressure test.

High Melting Point Grease was run through this test and scored a 100 Timken OK Load, a standout result. This same grease, when put through the ASTM D-1264 Water Washout Test, scored an astounding 0.65% water washout.

It is also important to choose the correct NLGI grade grease. NLGI is the acronym for the National Lubricating Grease Institute. The most common and general purpose  EP grease will be the NLGI 2 grade.

Bulldozer doing road construction in Himalayas.
An EP grease that is formulated with adhesive and cohesive additives give it a tacky property that creates a protective barrier to all parts from dust, dirt, mud, etc.








Compare those two scores to the industry standard of greases found in the market place. It is safe to say that there are specialized extreme pressure greases that could offer far superior protection for those pieces of equipment that are exposed to very extreme pressures and potentially high amounts of water exposure. The two go hand in hand.

So, what is EP grease best used for? If one considers investing in this type of grease, it can effectively be used for realizing much lower grease consumption, a vast reduction in breakdowns, lower repair costs, and prolonged equipment life.

Logging truck being unloaded.
Trucks hauling huge heavy logs will need a grease that can withstand extreme shock loads and extreme pressure. Conventional greases simply are not up to the task in protecting chassis parts.